docs: def sph2cart(r, az, elev):
      """ Convert spherical to cartesian coordinates.
  
      Attributes
      ----------
      r : float
          radius
      az : float
          aziumth (angle about z axis)
      elev : float
          elevation from xy plane
  
      Returns
      -------
      float
          x-coordinate
      float
          y-coordinate
      float
          z-coordinate
      """
      x = r * np.cos(az) * np.sin(elev)
      y = r * np.sin(az) * np.sin(elev)
      z = r * np.cos(elev)
      return x, y, z